Arnioceras semicostatoides Spath.
Very big calcitic Arnioceras on grey limestone. Free standing display specimen. Developed to the protoconch. A 'gem'.
Jurassic, Upper Sinemurian, Obtusum Zone.
Black Ven, Charmouth,/ Lyme Regis. Dorset.
Ammonite : 3.5 cm diam.
